diff --git a/cmd/restic/global.go b/cmd/restic/global.go
index 08b27ae4a..503cfe655 100644
--- a/cmd/restic/global.go
+++ b/cmd/restic/global.go
@@ -95,7 +95,7 @@ func init() {
 	f.CountVarP(&globalOptions.Verbose, "verbose", "v", "be verbose (specify --verbose multiple times or level `n`)")
 	f.BoolVar(&globalOptions.NoLock, "no-lock", false, "do not lock the repo, this allows some operations on read-only repos")
 	f.BoolVarP(&globalOptions.JSON, "json", "", false, "set output mode to JSON for commands that support it")
-	f.StringVar(&globalOptions.CacheDir, "cache-dir", "", "set the cache directory")
+	f.StringVar(&globalOptions.CacheDir, "cache-dir", "", "set the cache directory. (default: use system default cache directory)")
 	f.BoolVar(&globalOptions.NoCache, "no-cache", false, "do not use a local cache")
 	f.StringSliceVar(&globalOptions.CACerts, "cacert", nil, "`file` to load root certificates from (default: use system certificates)")
 	f.StringVar(&globalOptions.TLSClientCert, "tls-client-cert", "", "path to a file containing PEM encoded TLS client certificate and private key")
diff --git a/doc/manual_rest.rst b/doc/manual_rest.rst
index 8cdca465b..e1f2ef8fd 100644
--- a/doc/manual_rest.rst
+++ b/doc/manual_rest.rst
@@ -43,7 +43,7 @@ Usage help is available:
 
     Flags:
           --cacert file              file to load root certificates from (default: use system certificates)
-          --cache-dir string         set the cache directory
+          --cache-dir string         set the cache directory. (default: use system default cache directory)
           --cleanup-cache            auto remove old cache directories
       -h, --help                     help for restic
           --json                     set output mode to JSON for commands that support it
@@ -94,7 +94,7 @@ command:
 
     Global Flags:
           --cacert file              file to load root certificates from (default: use system certificates)
-          --cache-dir string         set the cache directory
+          --cache-dir string         set the cache directory. (default: use system default cache directory)
           --cleanup-cache            auto remove old cache directories
           --json                     set output mode to JSON for commands that support it
           --limit-download int       limits downloads to a maximum rate in KiB/s. (default: unlimited)